linux-kernel - [PATCH] x86/microcode/intel: Drop wbinvd(), no longer required

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Message-Id: <20220829182557.729300-1-ashok.raj@intel.com>
Date:   Mon, 29 Aug 2022 18:25:57 +0000
From:   Ashok Raj <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     "LKML Mailing List" <linux-kernel@...r.kernel.org>,
        X86-kernel <x86@...nel.org>, Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        "Ashok Raj" <ashok.raj@...el.com>, Tony Luck <tony.luck@...el.com>
Subject: [PATCH] x86/microcode/intel: Drop wbinvd(), no longer required

Some older processors had a bad interaction when updating microcode if the
caches were dirty causing machine checks. The wbinvd() was added to
mitigate that before doing microcode updates. Now that Linux checks for the
minimum version before performing an update, those old microcode versions
can't be loaded.  Remove calls to wbinvd().

Depends on Link below:

Link: https://lore.kernel.org/lkml/20220829180436.716672-1-ashok.raj@intel.com/T/#u
Reviewed-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Ashok Raj <ashok.raj@...el.com>
---
 arch/x86/kernel/cpu/microcode/intel.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 332ba19e0147..ae3c7ed15e79 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -536,12 +536,6 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 		return UCODE_OK;
 	}
 
-	/*
-	 * Writeback and invalidate caches before updating microcode to avoid
-	 * internal issues depending on what the microcode is updating.
-	 */
-	native_wbinvd();
-
 	/* write microcode via MSR 0x79 */
 	native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
@@ -758,12 +752,6 @@ static enum ucode_state apply_microcode_intel(int cpu)
 		goto out;
 	}
 
-	/*
-	 * Writeback and invalidate caches before updating microcode to avoid
-	 * internal issues depending on what the microcode is updating.
-	 */
-	native_wbinvd();
-
 	/* write microcode via MSR 0x79 */
 	wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
 
-- 
2.32.0